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Thursday, August 11, 2011
Air pollution and cancer incidence: a Danish cohort study
Air pollution is on the increase and so are the associated risks. It is a generally accepted fact that air in urban areas is polluted by mutagenic and carcinogenic substances, such as polycyclic aromatic hydrocarbons (PAHs).
Although the pollution caused by PAH in the atmosphere is not on par with cigarette smoke or some work environments in terms of concentration of carcinogenic substances, it definitely is harmful.
Ubiquitous air pollution, even at low levels, is a cause of public health concern because of the number of people who are exposed to it.
Ultrafine particles, < 100 nm in diameter, have large surface areas and are released in increased numbers from vehicular traffic.
They accumulate in the airways and then translocate to other organs such as the liver, kidneys, heart and brain.
Earlier studies have supported an association between air pollution and increased risk for lung cancer.
Some other cancers, such as those of the mouth, pharynx, larynx, kidney and bladder, have also been linked to air pollution.
Earlier studies have also confirmed that occupational areas with high levels of benzene are known to cause hematological (blood) cancers whereas occupational exposure to diesel engine exhaust may cause cervical, ovarian and stomach cancer.
The aim of the study reported here was to investigate in a large Danish cohort, whether air pollution near residence due to traffic was associated with risks for 20 selected, relatively frequent cancers found in that population.
Methods -During 1993–1997, 57,053 men (48%) and women (52%) between the age of 50–64 years, who were living in Copenhagen and Aarhus areas, were recruited for the Diet, Cancer and Health cohort study.
The study included a questionnaire on dietary habits, (which covered 192 food and beverage items), their smoking habits (status, intensity, and duration), occupation, length of school attendance, reproductive factors, history of diseases and medication, and a varied number of other health-related items.
Follow-ups were calculated for each cohort member until 27 June 2006 based on the information got from the Danish Cancer Registry and the Danish Pathology Data Bank.
The end-points for the risk analyses were primary cancers rather than lung cancer.
The significance of this study was that it included a 10-year prospective follow-up of a relatively large cohort.
- Result & conclusion
The study found significant associations between traffic-related air pollution at the residence for several decades and risks for cervical cancer and brain cancer.
The study discovered a border line significantly increased risk for liver cancer associated with traffic pollution within 200 m of the residence.
The study also showed that the risk for kidney cancer increased with increased nitrous oxide concentration near the residence.
However, there was a weak, insignificant association between traffic-related air pollution and breast or bladder cancer risk.
Further studies are required to confirm possible risks for other cancers.